Wal-Mart announced plans to test two different hybrid trucks and three different types of alternative fuels in an effort to double their fleet’s fuel efficiency. The company has already achieved a 25 percent increase in efficiency with its private fleet of trucks between 2005 and 2008. It hopes to double that by 2015.

Wal-Mart, which operates one of the largest private truck fleets in the world, will this year retrofit a portion of its fleet to run on reclaimed grease fuel from Wal-Mart and Sam’s Club locations. Trucks in Arizona will operate on an 80/20 blend of biodiesel made from cooking oil waste. Others will be tested on liquefied natural gas.